Optical networks form the backbone of today's telecommunication and data network infrastructure. Optical networks are formed by interconnecting nodes (referred to herein as network elements, or NE) with optical fiber segments. Coherent (laser) light transmits information among the nodes and along the segments. The first optical networks used a single wavelength of light to convey information among its nodes. More modern optical networks employ wavelength division multiplexing (WDM), in which multiple wavelengths of light form separate channels through the fibers, allowing the same optical fibers to support significantly greater data rates. Dense WDM, or DWDM, packs the multiple wavelengths less than 100 GHz apart and as a result provides data rates that exceed those of WDM (now called coarse WDM, or CWDM).
Resources are located at the nodes (NEs) or along the segments of an optical network. These resources process the light in various ways and include, for example, passive elements such as optical multiplexers/demultiplexers (called “OMDs” or, more colloquially, “muxes”) that combine or separate different wavelengths of light, and active elements, such as amplifiers that amplify optical signals, transponders that convert light from one wavelength to another and are typically used to add specific wavelengths to or drop specific wavelengths from a segment of the optical network, time-domain multiplexers/demultiplexers that combine or separate optical signals based on time, transmitters that convert electrical signals to optical form and receivers that convert optical signals back into electrical signals.
From a physical perspective, resources located at edges of the network (e.g., customer premises) take the form of chassis or more appropriately electronics enclosure often called optical network units (ONUs), or optical network terminals (ONTS). Resources located in more central locations (e.g., central offices, or COs) may also take the form of chassis, but they can also take the form of cards that are mounted in slots of chassis called shelves and sub-cards that may be mounted in portions of the cards called drawers. The shelves themselves may be divided into sub-shelves. The shelves are mounted on vertical racks. Depending upon its complexity, a node often has more than one shelf and, indeed, may have more than one rack.
Optical interfaces to the chassis, cards or sub-cards are called ports and are physically manifested in adapters. Adapters feed through walls of the chassis or are provided on the front edges of the cards or sub-cards to receive optical fibers. Some chassis, cards or sub-cards have only one adapter; others have many, depending on the function performed. Optical connections are made to these adapters. Other adapters are not associated with a chassis, card or sub-card and allow one fiber to be connected directly to another to form a longer fiber.
As those skilled in the art are aware, it is important that the optical connections be of high integrity so as to lose as little signal as possible. A variety of connectors exist to make high quality optical connections. Sugita, et al., “SC-Type Single-Mode Optical Fiber Connectors,” Journal of Lightwave Technology, Vol. 7, No. 11, November 1989, pp. 1689-1696, incorporated herein by reference, describes one prevailing connector, an SC connector. A variation of the SC connector, an SC/APC connector, provides an angled polish contact for the fiber. U.S. Pat. No. 6,926,449, which issued to Keenum, et al., on Aug. 9, 2005, entitled “Connector Port for Network Interface Device” and incorporated herein by reference, describes another prevailing connector, a “ruggedized” version of the SC connector. According to the patent, the “ruggedized” SC connector is water resistant and weatherproof and permits less experienced and less skilled technicians to connect, disconnect and reconfigure optical connections in the field.